This invention relates to video signal processing and especially to processes of interpolation, particularly spatial interpolation, whether horizontal, vertical or two dimensional. The invention applies in an important example to the process of de-interlacing by which a video frame is derived for each field of an interlaced video signal.
A known de-interlacing technique derives the xe2x80x9cmissingxe2x80x9d lines through a weighted sum of neighbouring sample points. The location of the sample points to be employed and the values of the weighting coefficients are chosen to minimise visual artefacts and certain design principles have been established.
Adaptive techniques have emerged by which the characteristics of the de-interlacing filter are changed in the face ofxe2x80x94for examplexe2x80x94motion.
It is an object of aspects of the present invention to provide improved video signal processing by which the appearance of visual artefacts on spatial interpolation is further minimised.
It is a further object of one aspect of the present invention to provide improved video signal processing by which a video frame is derived for each field of an interlaced video signal.
Accordingly, the present invention consists in one aspect in a video process wherein a weighted sum of pixels from at least one input picture is taken in a filter aperture to generate a pixel in an output picture, characterised in that the weighted sum includes products of triplets of pixels.
Suitably, a video frame is derived through spatial interpolation from each video field of an interlaced input signal.
In one form of the invention, the weighted sum comprises pixels and products of triplets of pixels.
In another aspect, the present invention consists in a video process of interpolation, wherein adaption is provided between a process of spatial interpolation in which a weighted sum of products of pixels from an input picture is taken in a filter aperture to generate a pixel in an output picture, and a process of temporal interpolation which a weighted sum of pixels from two or more input pictures is taken in a filter aperture to generate a pixel in an output picture.
In yet another aspect, the present invention consists in video signal processing apparatus for interpolation, comprising an interpolation filter taking a weighted sum of pixels from at least one input picture in a filter aperture, to generate a pixel in an output picture, characterised in that the weighted sum includes products of triplets of pixels.